Summary of important user-visible changes for version 4.2:
---------------------------------------------------------

 ** Interpolation function changes for Matlab compatibility

    The interpolation method 'cubic' is now equivalent to 'pchip'
    for interp1, interp2, and interp3.  Previously, 'cubic' was equivalent
    to 'spline' for interp2.  This may produce different results as 'spline'
    has continuous 1st and 2nd derivatives while 'pchip' only has a continuous
    1st derivative.

 ** Integer formats used in the printf family of functions now work for
    64-bit integers and are more compatible with Matlab when printing
    non-integer values.  Now instead of truncating, Octave will switch
    the effective format to '%g' in the following circumstances:

      * the value of an integer type (int8, uint32, etc.) value exceeds
        the maximum for the format specifier.  For '%d', the limit is
        intmax ('int64') and for '%u' it is intmax ('uint64').

      * round(x) != x or the value is outside the range allowed by the
        integer format specifier.

    There is still one difference:  Matlab switches to '%e' and Octave
    is currently switching to '%g'.

 ** linkprop has been completely re-coded for performance and Matlab
    compatibility.  It now returns a linkprop object which must be stored
    in a variable for as long as the graphic objects should remain linked.
    To unlink properties use 'clear hlink' where hlink is the variable
    containing the linkprop object.

 ** Other new functions added in 4.2:

      dir_in_loadpath    numfields
      hgload
      hgsave
      javachk
      linkaxes 

 ** Deprecated functions.

    The following functions have been deprecated in Octave 4.2 and will
    be removed from Octave 4.6 (or whatever version is the second major
    release after 4.2):

      bicubic
      find_dir_in_path
      nfields

    The following functions were deprecated in Octave 3.8 and have been
    removed from Octave 4.2.

      default_save_options    java_new            
      gen_doc_cache           java_set                   
      interp1q                java_unsigned_conversion
      isequalwithequalnans    javafields                
      java_convert_matrix     javamethods               
      java_debug              re_read_readline_init_file
      java_get                read_readline_init_file   
      java_invoke             saving_history            

    The following keywords were deprecated in Octave 3.8 and have been
    removed from Octave 4.2

      static

    The following configuration variables were deprecated in Octave 3.8
    and have been removed from Octave 4.2

      CC_VERSION  (now GCC_VERSION)
      CXX_VERSION (now GXX_VERSION)

    The internal class <Octave_map> was deprecated in Octave 3.8 and has
    been removed from Octave 4.2.  Replacement classes are
    <octave_map> (struct array) or <octave_scalar_map> for a single structure.

Summary of important user-visible changes for version 4.0:
---------------------------------------------------------

 ** For compatibility with Matlab, the "backtrace" warning option is now
    enabled by default.

 ** The preference

      do_braindead_shortcircuit_evaluation

    is now enabled by default.

 ** The preference

      allow_noninteger_range_as_index

    is now enabled by default and the warning ID

      Octave:noninteger-range-as-index

    is now set to "on" by default instead of "error" by default and "on"
    for --traditional.

 ** polyeig now returns a row vector of eigenvalues rather than a matrix
    with the eigenvalues on the diagonal.  This change was made for Matlab
    compatibility.

 ** Other new functions added in 4.0.0:

      validateattributes

 ** Deprecated functions.

    The following functions were deprecated in Octave 3.6 and have been
    removed from Octave 4.0.
                                           
      cut                polyderiv        
      cor                shell_cmd        
      corrcoef           studentize       
      __error_text__     sylvester_matrix 
      error_text         

    The following functions have been deprecated in Octave 4.0 and will
    be removed from Octave 4.4 (or whatever version is the second major
    release after 4.0):

      allow_noninteger_range_as_index
      do_braindead_shortcircuit_evaluation
      
    The internal function atan2 of the sparse matrix class has been deprecated
    in Octave 4.0 and will be removed from Octave 4.4 (or whatever version is
    the second major release after 4.0).  Use the Fatan2 function with sparse
    inputs as a replacement.

---------------------------------------------------------

See NEWS.3 for old news.